Biology subjects

Dudycha, J. L.

Publications and source records attributed to Dudycha, J. L..

4 recordsLinked to original sources

bioRxiv2025

Light color and nutrients interact to determine freshwater algal community diversity and composition

Lakes experience a wide range of variation in resource availability; variation of essential resources such as light and nutrients can cause changes in algae community structure. Changes in light color and nutrient availability could lead to shifts in algal community diversity and composition, including shifting communities to be dominated by cyanobacteria. Due to eutrophication and brownification, lakes are experiencing increases in nutrient concentrations and shifts from blue towards red in the color of light available to algae for photosynthesis. We investigated whether differences in light color and nutrients affect algal community composition and diversity, and whether differences in light color alter the impact that nutrient levels have on algal communities. We used experimental microcosms with a fully factorial experimental design, crossing four light colors with two nutrient levels. We assessed community composition by enumerating algal taxa via light microscopy. We found that light color and the interaction between light color and nutrient availability led to large differences in community diversity, with blue light leading to the greatest diversity and broad light the lowest. Light color, nutrients, and the interaction between the two were all significant drivers of differences in community composition. Overall, we found that light color and nutrient availability interact to affect algal community diversity, composition, and cyanobacteria density. Consequences of light color are infrequently studied in aquatic ecology, but our results show that light color may need to be considered more broadly. Furthermore, our results suggest that concurrent eutrophication and brownification may yield environmental conditions favorable to cyanobacteria, including taxa that can form harmful algal blooms.

ecology↗

bioRxiv2023

Consequences of light spectra for pigment composition and gene expression in the cryptophyte Rhodomonas salina

SummaryAlgae with a more diverse suite of pigments can, in principle, exploit a broader swath of the light spectrum through chromatic acclimation, the ability to maximize light capture via plasticity of pigment composition. We grew Rhodomonas salina in wide-spectrum, red, green, and blue environments and measured how pigment composition differed. We also measured expression of key light-capture and photosynthesis-related genes and performed a transcriptome- wide expression analysis. We observed the highest concentration of phycoerythrin in green light, consistent with chromatic acclimation. Other pigments showed trends inconsistent with chromatic acclimation, possibly due to feedback loops among pigments or high-energy light acclimation. Expression of some photosynthesis-related genes was sensitive to spectrum, although expression of most was not. The phycoerythrin -subunit was expressed two-orders of magnitude greater than the {beta}-subunit even though the peptides are needed in an equimolar ratio. Expression of genes related to chlorophyll-binding and phycoerythrin concentration were correlated, indicating a potential synthesis relationship. Pigment concentrations and expression of related genes were generally uncorrelated, implying post-transcriptional regulation of pigments. Overall, most differentially expressed genes were not related to photosynthesis; thus, examining associations between light spectrum and other organismal functions, including sexual reproduction and glycolysis, may be important. Originality-Significance StatementMost work on light and algal photophysiology focuses on light intensity rather than light spectrum. Given the large spectral variation of light in aquatic systems, explaining how such algae respond to spectral variation will provide a better foundation for understanding the base of aquatic food webs. Much of the light spectrum is poorly absorbed by chlorophyll, which creates an opportunity for photosynthetic species with other pigments. We quantified physiological and genetic responses to light spectrum in replicate experimental populations of Rhodomonas salina, an alga with a phycoerythrin in addition to chlorophylls. We predicted photophysiology and gene expression would change to maximize R. salinas capacity to capture available light, in accordance with the theory of chromatic acclimation. Our results show that responses to light spectra are more complex than predicted. Some aspects of photophysiology did support the theorys predictions, but gene expression was generally unrelated to variation of light spectrum or photophysiology. This not only suggests that chromatic acclimation is potentially regulated post-transcriptionally, but also that physiological processes - notably glycolysis and the transition to sexual reproduction - that may be regulated by light spectrum. Our work adds to the generally limited work on light spectrum and physiology by investigating a eukaryote from a phylum with a great diversity of photosynthetic pigments.

ecology↗

bioRxiv2023

A three-genome ultraconserved element phylogeny of Cryptophytes

Cryptophytes are single celled protists found in all aquatic environments. They are composed of a heterotrophic genus, Goniomonas, and a largely autotrophic group comprising many genera. Cryptophytes evolved through secondary endosymbiosis between a host eukaryotic heterotroph and a symbiont red alga. This merger resulted in a four-genome system that includes the nuclear and mitochondrial genomes from the host and a second nuclear genome (nucleomorph) and plastid genome inherited from the symbiont. Here, we make use of different genomes (with potentially distinct evolutionary histories) to perform a phylogenomic study of the early history of cryptophytes. Using ultraconserved elements from the host nuclear genome and symbiont nucleomorph and plastid genomes, we produce a three-genome phylogeny of 91 strains of cryptophytes. Our phylogenetic analyses find that that there are three major cryptophyte clades: Clade 1 comprises Chroomonas and Hemiselmis species, Clade 2, a taxonomically rich clade, comprises at least twelve genera, and Clade 3, comprises the heterotrophic Goniomonas species. Each of these major clades include both freshwater and marine species, but subclades within these clades differ in degrees of niche conservatism. Finally, we discuss priorities for taxonomic revision to Cryptophyceae based on previous studies and in light of these phylogenomic analyses.

evolutionary biology↗

bioRxiv2023

A test of the gleaner-opportunist trade-off among photosynthetic traits in Cryptophyte algae

As photosynthetic producers, phytoplankton form the foundation of aquatic food webs. Understanding the relationships among photosynthetic traits in phytoplankton is essential to revealing how diversification of these traits allow phytoplankton to harvest energy from different light environments. We investigated whether the diversification of 15 species of cryptophytes, a phylum of phytoplankton with diverse light-capturing pigments, showed evidence of trade-offs among photosynthetic performance traits as predicted by the gleaner-opportunist resource exploitation framework. We constructed photosynthesis vs. irradiance (P-E) curves and rapid light curves (RLCs) to estimate parameters characterizing photosynthetic performance and electron transport rate. We inferred the evolutionary relationships among the 15 species with ultraconserved genomic elements and used a phylogenetically controlled approach to test for trade-offs. Contrary to our prediction, we observed a positive correlation between maximum photosynthetic rate, Pmax, and P-E , an indicator of a species sensitivity to increases in light intensity when light is a scarce resource. This result could not be explained by electron transfer traits, which were uncorrelated with photosynthetic rate. Together, our results suggest that ecological diversification of light exploitation in cryptophytes has escaped the constraints of a gleaner-opportunist tradeoff. Photosynthetic trade-offs may be context or scale dependent, thereby only emerging when investigated in situations different from the one used here.

ecology↗